The invention pertains to apparatus for monitoring the operation of electromagnets. More specifically, the invention is directed to apparatus for monitoring the operation of electromagnetic type solenoid valves in motor vehicle brake systems.
The operability condition and/or the response to demand of electromagnets in the solenoid valves controlling the brakes of motor vehicles is of primary importance in the operational safety of such vehicles. Apparatus for detecting discontinuities in the electrical control circuits for such solenoid valves or in the winding of the electromagnet and for detecting short circuits in the leads or coil windings is known in the art. However, proper operation of the solenoid valve may be prevented by partial shorts in the magnet winding which are not detectable by the available checking apparatus. Also, mechanical problems or faults may prevent operation of the valve. For example, the armature controlled by the electromagnet may stick or be rusted in place, due to corrosion factors such as winter salt use or industrial gases. This type of failure is critical on brake valves which are infrequently used. Additional fault detecting or monitoring apparatus for these conditions is desirable.
Accordingly, an object of the invention is improved apparatus for monitoring the operation of electromagnets.
Another object of the invention is apparatus for detecting the failure of the electromagnet armature of a solenoid valve to operate when energy is applied.
A further object of the invention is a circuit arrangement which detects the movement of the armature of an electromagnet in accordance with energizing current variations to reset a memory unit prior to the expiration of a preset timing period running from the initial energization of the electromagnet and indicates a fault condition when no movement is detected during the timing period.
Other objects, features, and advantages of the invention will become apparent from the following specification and appended claims, when taken in connection with the accompanying drawing.